Chromosomal rearrangements, resulting in the deletion of segments of DNA, have been shown to lead to a number of different inheritable disease states in humans. The goal of this grant is to study deletions, in both the Alpha- and Beta-globin gene clusters, which seem to have been produced by non-homologous recombination and to begin to elucidate the machanism(s) responsible for producing these deletions. Previous work on four large deletion Beta-hemoglobinopathies (two GammaDeltaBeta-thalassemias and two HPFHs) has shown that for each pair of deletions the 5' breakpoints are in the same order along the DNA and approximately the same distance apart as their 3' breakpoints. Hence for deletions extending in the same direction from the Beta-globin cluster the amount of DNA deleted is the same. Additional deletions will be studied in order to determine whether they fall into the same or different pattern than that described above with a view to understanding the mechanism(s) underlying their formation. Four large deletion Alpha-thalassemias (Mediterranean, Asian, Black and Czech) will be examined in order to determine whether the same constant size deletion phenomenon is occuring in gene clusters other than the Beta-globin gene cluster. We will also study two new GammaDeltaBeta-thalassemias (GammaDeltaBeta-thalassemias 3 and 4). These two new GammaDeltaBeta-thalassemias provide an interesting problem in that the deletions extend in the same direction as those of GammaDeltaBeta-thalassemias 1 and 2 yet they do not obey the relationship seen for GammaDeltaBeta-thalassemias 1 and 2; more DNA is deleted in the two new GammaDeltaBeta-thalassemias. Results from these studies will enable us to determine how the two new GammaDeltaBeta-thalassemias are related to one another and also to GammaDeltaBeta-thalassemias 1 and 2. During the analysis of these different deletions we will sequence the normal 5', the deletion joint and the normal 3' DNAs. Comparison of these three sequences with one another will enable us to determine whether the recombinantional event was "clean." Comparison of the normal 5' and 3' sequences will determine whether there is any homology between the two sequences involved in creating the deletions; that is are these deletions the result of homologous or non-homologous recombination. Comparison of all the normal 5' and 3' sequences against one another will also give some insight into whether there are features in the sequences which predisposes them to breakage.